I drilled holes to drain it and caked the area with grease to stop rust.
did you drill a hole clear through towards the wheel well opening? i'm afraid to put holes in the car down there, but I have a decent amount of water pooled up in my jack compartment.
I had the same problem. Seamed to be water was leaking down the edge of the back hatch and leaking through the bolt holes for the taillights. I took them am siliconed them so they wouldn't leak. Seems to have worked for me.